One type of liquid crystal device to which the invention is applicable is the surface stabilised ferroelectric liquid crystal display (SSFLCD) which can be switched between two states by DC pulses of alternate sign. Such devices, containing ferroelectric liquid crystals in their smectic phase, are of interest particularly because of their speed of switching and their property of bi-stability, in other words they will remain in a particular state in the absence of a particular drive voltage. These devices have traditionally been driven using square wave voltage pulses since these pulses can readily be provided by circuitry of low complexity and have provided adequate performance. One such prior art drive scheme is described in, The "JOERS/Alvey" Ferroelectric Multiplexing Scheme published in Ferroelectrics, 1991, Vol. 122, pp. 63-79 by Gordon and Breach Science Publishers S.A. However, it has been realised that this type of drive technique results in limitations in device performance, particularly with respect to the switching speed between states of the liquid crystal pixels.
It is an object of the present invention to provide a liquid crystal device having a driving technique which ameliorates this drawback.
It is a further object of the invention to provide novel driving circuitry for use with a liquid crystal array to ameliorate the above drawback.
It is a still further object of the invention to provide a method of driving a liquid crystal device that ameliorates the aforementioned drawback.